The aim of this program is to develop an instrument suitable for screening the carotid artery for stenoses that lead to stroke. In the last decade it was shown that removal of high grade carotid stenoses could reduce the stroke rate in that population by more than 50%; as strokes caused by such stenoses are associated with 120,000 strokes per year, reducing these strokes by more than half is a desirable health care objective. Using Doppler information to detect high-grade stenosis with duplex ultrasound has been shown to have excellent screening sensitivity and specificity; however, the high cost of examination and the dependence on the operator/instrument for satisfactory performance has precluded stroke-preventing carotid screening. A new Doppler ultrasound method has been devised to measure blood velocity in the carotids without the need for imaging and with minimal dependence on its operator. In Phase I, the feasability of this method is to be demonstrated with a proof-of-concept instrument that will measure blood velocity and in its operation, its potential for operator-independence and low cost. The specific Milestone to be met in Phase I will be correlation of > .9 between the blood velocitiesit measures and those of a conventional duplex ultrasound examination in a group of patients already scheduled for such a duplex examination. In Phase II, the method proven in Phase I will be built into a prototype screening system, in collaboration the Center for Integration in Medicine of Innovative Technology (a MGH/Brigham & Women's/MIT/Draper Lab joint center) who will design and supervise the screening trials for the system and will shape the user interface/machine intelligence aspects of the prototype. Welch Allyn, who serves the 25,000+ primary care centers for whom this instrument is intended, will serve as an advisor in Phase II to ensure its path to commercial viability.